# Common PHP question asked in interview

21. What is the main difference between require() and require_once()?
require() and require_once() perform the same task except that the second function checks if the PHP script is already included or not before executing it.
(same for include_once() and include())

22. How can I display text with a PHP script?
Two methods are possible:


<?php echo "Method 1"; print "Method 2"; ?>



23. How can we display information of a variable and readable by human with PHP?
To be able to display a human-readable result we use print_r().

24. How is it possible to set an infinite execution time for PHP script?
The set_time_limit(0) added at the beginning of a script sets to infinite the time of execution to not have the PHP error ‘maximum execution time exceeded’.It is also possible to specify this in the php.ini file.

25. What does the PHP error ‘Parse error in PHP – unexpected T_variable at line x’ means?
This is a PHP syntax error expressing that a mistake at the line x stops parsing and executing the program.

26. What should we do to be able to export data into an Excel file?
The most common and used way is to get data into a format supported by Excel. For example, it is possible to write a .csv file, to choose for example comma as separator between fields and then to open the file with Excel.

27. What is the function file_get_contents() usefull for?
file_get_contents() lets reading a file and storing it in a string variable.

28. How can we connect to a MySQL database from a PHP script?
To be able to connect to a MySQL database, we must use mysql_connect() function as follows:


<?php $database = mysql_connect("HOST", "USER_NAME", "PASSWORD"); mysql_select_db("DATABASE_NAME",$database); ?>



29. What is the function mysql_pconnect() usefull for?
mysql_pconnect() ensure a persistent connection to the database, it means that the connection do not close when the the PHP script ends.

30. How the result set of Mysql be handled in PHP?
The result set can be handled using mysql_fetch_array, mysql_fetch_assoc, mysql_fetch_object or mysql_fetch_row.